In order to detect and analyze breast cancer, various mammography systems are known.
Besides conventional mammography screening systems (planar mammography), which require compressing the female breast between two plates and which are used for creating two-dimensional X-ray images with a high lateral resolution, digital breast tomosynthesis (DBT) mammography systems are known, that also realize depth resolution and relax the requirement of strongly compressing the breast during examination, as well as breast computer tomography (CT) systems.
In planar mammography currently energy resolving photon counting detectors of sufficient size for mammography are unavailable. Due to the large volume irradiated when acquiring a projection image a scatter grid is necessary for reducing scatter in the projection images.
In DBT systems, a plurality of X-ray images may be acquired while the breast is irradiated with an X-ray beam from a plurality of tomographic angles. Conventionally, an X-ray source is moved along a circular arc path while being always oriented towards a fixed detector above which the breast is supported. Conventionally, X-ray images are acquired within a range of tomographic angles of exemplarily up to 2×25°. From the plurality of acquired two-dimensional X-ray images, a final three-dimensional volume of the breast may be generated. Such a three-dimensional volume may provide for both, good lateral resolution and sufficient depth resolution, wherein the depth resolution typically increases reciprocally proportional with the range of tomographic angles.
Multi-slit X-ray scanning systems are known, which comprise a detector having a plurality of detector strips and associated read-out electronics. A pre-collimator having multiple slits at the projections of these detector strips is provided. A further collimator is placed between breast and detector to remove radiation that is scattered in the tissue.
However, it may be difficult to design a multi-slit scanning system which is able to perform a large angle tomosynthesis scan and a projection mammography at the same time. Furthermore, breast biopsies may be hard to realize on these systems since a necessary pre-collimator may hamper the installation of a biopsy unit in the most natural position. Also, high tube power is required since the pre-collimator limits the tube output to the detector lines of the photon counting detector.